A proportion of all oil and gas wells eventually require some form of stimulation to enhance their hydrocarbon flow and make them economically viable. Stimulation of an oil or gas well may be accomplished by several methods. One method involves pumping an acidic solution under pressure into the hydrocarbon bearing formation of a well. Another method is to hydraulically fracture the hydrocarbon bearing formations of a well. Hydraulic fracturing is the process of breaking open a hydrocarbon bearing formation by forcing into it liquids and/or gases which may be laden with abrasives. Extremely high pressures and high flow rates must be employed in the hydraulic fracturing process.
The conventional wellhead assembly, commonly called a well tree, installed on most oil and gas wells is generally not designed to withstand the pressures required to hydraulically fracture a well or, in some cases, to inject caustic fluids into a well. Most conventional well trees are designed for pressures of 21,000 kPa or less while pressures in excess of 21,000 kPa are often required in the hydraulic fracturing process. Therefore, to stimulate a well, the well tree must either be upgraded to the necessary pressure requirements or it must be isolated from the elevated pressures required for the well stimulation process.